Multifunctional optical assembly

ABSTRACT

An optical assembly including a light management component and a light delivery component is disclosed. The light management component and the light delivery component are attached together in a manner that defines voids between the light management component and the light delivery component.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of application U.S. Ser.No. 11/456993 filed Jul. 12, 2006, now allowed, which is a Divisional ofapplication U.S. Ser. No. 11/297,607, filed on Dec. 8, 2005; which is aDivisional of U.S. Ser. No. 10/156,674 filed May 28, 2002, now issued,as U.S. Pat. No. 7,010,212, issued on Mar. 7, 2006, the disclosures ofall of which are herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to an optical assembly. Moreparticularly, the invention relates to a multifunctional opticalassembly for use in a display system.

BACKGROUND

A typical optical display system contains a light source that isrequired to observe the information presented by the display. In batterypowered equipment like laptop computers, the light source can representa substantial fraction of the total power draw of the equipment.Therefore, reducing the amount of power required to produce a givenluminance can increase battery life, which may be especially desirablein battery powered equipment.

The 3M brand Brightness Enhancement Film (BEF) available from the 3MCompany of St. Paul, Minn., is one type of optical film that can be usedto address this problem. BEF and similar films typically include anarray of prisms on one surface that are large in comparison with thewavelengths of light. The structures can increase on-axis brightness ofoptical display systems by redirecting off-axis light and recycling theon-axis light such that it eventually emerges from the display on-axis,i.e., generally directed toward a viewer. In use, these films typicallyincrease on-axis luminance at the expense of off-axis luminance in oneor two dimensions. In this fashion, the material can help the displaydesigner achieve the desired amount of on-axis luminance with reducedpower consumption. Various embodiments of BEF and other similar filmshaving structured surfaces are described in, e.g., U.S. Pat. No.5,394,255 (Yokota et al.); U.S. Pat. No. 5,552,907 (Yokota et al.); U.S.Pat. No. 5,917,664 (O'Neill et al.); U.S. Pat. No. 6,052,164 (Cobb, Jr.et al.); U.S. Pat. No. 6,091,547 (Gardiner et al.); and U.S. Pat. No.6,111,696 (Allen et al.).

Brightness enhancement is achieved with such prismatic structuredsurface films through a process of reflection and refraction thatpreferably includes light recycling. When used in preferred backlightconfigurations, prismatic structured surface films transmit light in thedirection of the viewer (usually directly in front of the LCD) thatwould otherwise leave the screen at a high angle (missing the viewer).

In order for a prismatic structured surface film to direct light into anarrower angular exit profile toward the user, the film often includes aplanar or nearly planar entry surface (on the opposite side of the filmfrom the prisms) that includes an interface with air or another materialwith a sufficiently low index of refraction. The entry surface generallyprohibits light from entering the film at internal angles greater thanabout 40 degrees from a normal direction defined by the entry surface.

To operate more efficiently, the entry surface of the prismaticstructured surface film is typically separated by an air gap from othercomponents in the display system so that the refraction characteristicsof light entering the prismatic structured surface film through itsentry surface are not affected by the generally higher indices ofrefraction of, e.g., a diffusing layer, light guide, etc. For example,air has an index of refraction of one (1), while polymers used toconstruct the diffusing layers typically have a higher index ofrefraction that is closer to the index of refraction of the materialsused to manufacture the prismatic structured surface film. As a result,light refraction at a polymer interface is different than refraction oflight at an air interface. Current techniques for manufacturing opticaldisplay systems that include prismatic structured surface films withentry surfaces commonly rely on the air gaps that will inherently existbetween two films layered with each other in the absence of an adhesiveor other agent that would optically couple the two layers.

This approach can, however, increase the cost of assembling the opticaldisplay because of the need to assemble the prismatic structured surfacefilm with the other components in the optical display system. Thelayering approach may also lead to inconsistencies in appearance of theoptical display as the air gap between the entry surface of theprismatic structured surface film and other components adjacent theentry surface varies over the entry surface. For example, in some areasthe entry surface may be in contact with an adjacent component in amanner that negatively affects the refraction of light into film at theentry surface.

SUMMARY OF THE INVENTION

The present invention provides an integrated optical assembly includinga light management component with an entry surface and a light deliverycomponent having an exit surface attached to the entry surface of thelight management component. The light management component and the lightdelivery component are attached together in a manner that defines voidsbetween the entry surface of the light management component and the exitsurface of the light delivery component.

The voids between the light management component and the light deliverycomponent may provide advantages when the light management component isconstructed in a manner such that its functioning is improved when,e.g., an air interface, can be maintained over substantial portions ofthe entry surface. Although the voids may often be occupied by air, itwill be understood that any other gas or gases that provide a desirableindex of refraction differential with the entry surface may occupy thevoids. For example, the voids may be occupied by one or more gases otherthan air. Furthermore, although the voids may be referred to in theplural, it should be understood that the voids as depicted in thefigures described below may, in fact, be part of a continuous voidinterrupted by structures designed to maintain the void(s) between thelight management component and the light delivery component.

As a result, optical film assemblies according to the present inventionmay substantially retain the refraction characteristics of the lightmanagement component while providing an integrated multifunctionaloptical assembly.

As used herein, a “light management component” is defined as an opticaldevice (film, body, etc.) that is operable to direct at least a portionof incident light in a desired direction or directions throughrefraction, reflection, total internal reflection, and/or frustratedtotal internal reflection.

As used herein, a “light delivery component” is an optical device (film,body, etc.) that includes an exit surface, with light exiting the exitsurface and traveling towards the entry surface of the light managementcomponent. Light may also exit other surfaces of the light deliverycomponent.

The light management component and/or the light delivery component (whenapplicable) used in connection with an optical assembly according to thepresent invention may be described as exhibiting optical gain asdescribed in U.S. Pat. No. 5,917,664 (O'Neill et al.). The optical gainis preferably one (1) or higher.

Because the light management component and the light delivery componentare attached to each other into an integrated optical assembly,manufacturing may be simplified, the integrity of both components (thelight management component and the light delivery component) may beimproved, and the cost of optical display systems incorporating theintegrated optical assemblies may be decreased.

In one aspect, the present invention provides an optical assemblyincluding a light management component with an entry surface and a lightdelivery component with an exit surface facing the entry surface of thelight management component. The exit surface of the light deliverycomponent is attached to the entry surface of the light managementcomponent at one or more attachment points, the one or more attachmentpoints defining unfilled voids located between the exit surface and theentry surface. One or both of the light management component and thelight delivery component exhibit an optical gain of one or more.

In another aspect, the present invention provides an optical assemblyincluding a light management component with an entry surface, whereinthe light management component exhibits an optical gain of one or morefor light entering its entry surface. The optical assembly also includesa release liner facing the entry surface of the light managementcomponent and curable adhesive located between the release liner and theentry surface of the light management component, wherein the curableadhesive is attached to the entry surface and defines voids between therelease liner and the entry surface of the light management component.

These and other features and advantages of the invention may bedescribed below in connection with some illustrative embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of one optical assembly according to thepresent invention.

FIGS. 1-12 are partial cross-sectional diagrams of various illustrativeoptical assemblies according to the present invention.

FIG. 13 is a diagram of one optical display system including an opticalassembly according to the present invention.

FIGS. 14A-14C are partial cross-sectional diagrams of one method offorming a structure for use in an optical assembly according to thepresent invention.

FIGS. 15 & 16 are partial cross-sectional diagrams of curable adhesivesand liners attached to a light management component in accordance withthe present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

In the following detailed description of the embodiments, reference ismade to the accompanying drawings which form a part hereof, and in whichare shown, by way of illustration, specific embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

In some embodiments, the present invention as depicted in FIG. 1Aprovides an optical assembly 10′ that includes a light managementcomponent 20′ integrated with a light delivery component 30′. Theattachment between the two components 20′ and 30′ is such that voids 41′are created between them and between attachment points 40′ at which thelight management component 20′ and the light delivery component 30′ areattached.

The voids 41′ are unfilled voids, i.e., they typically include one ormore gases such as, e.g., air, nitrogen, etc. The unfilled voids 41′preferably have an index of refraction that is substantially less thanthe surrounding materials, in some instances, for example, it may bepreferred that the voids have an index of refraction of about one (1).

In many instances, the light management component relies on therefraction of light entering an entry surface such that the lightexiting from an exit surface of the light delivery component isredirected into, e.g., a desired range of angles that may, e.g., enhanceviewing, brightness, etc. In many instances, it may be desirable thatthe refractive index differential at the entry surface of the lightmanagement component be relatively large. For example, it may bedesirable that the light management component be manufactured of apolymer or other material with a relatively high index of refraction(e.g., polycarbonate with an index of refraction of 1.586) and that theentry surface be exposed to air (with its refractive index of 1.0). Suchan interface may attain a desired level of refraction for light enteringthe light management component through its entry surface.

The light delivery component may be, e.g., a diffuser to diffuse lightbefore it enters the entry surface of the light management component.The diffusion may be provided to, e.g., obscure features, homogenize thelight, change the dispersion of light exiting the light deliverycomponent, change the approach angle of light incident on the entrysurface of the light management component, etc. In another alternative,the light delivery component may be, e.g., a light guide that provideslight distributed over the entry surface of the light managementcomponent.

Because the refraction characteristics of light at an interface are afunction of the ratio of indices of refraction at that interface,spacing between the light management component and the light deliverycomponent may be used to control the performance of the optical assemblyas a whole. In many instances, the light management component and thelight delivery component may often be manufactured of materials withsimilar indices of refraction. As a result, areas of contact between theentry surface of the light management component and the light deliverycomponent will exhibit a smaller index of refraction differential thanwould be seen between, e.g., an air/entry surface interface. Thatsmaller index of refraction differential may negatively affectperformance of the light management component and, thus, the opticalassembly as a whole.

To retain the refraction characteristics of light entering the entrysurface of the light management component, the present inventionincludes unfilled voids between the entry surface of the lightmanagement component and the exit surface of the light deliverycomponent. Outside of the portions of the entry surface occupied by thevoids, substantially all of the exit surface of the light deliverycomponent is preferably attached to the entry surface of the lightmanagement component within the optical assembly.

The voids may be defined, in some embodiments, by spacers locatedbetween the light management component and the light delivery component,with the spacers occupying a portion of the volume between the lightmanagement component and the light delivery component. In manyinstances, the spacers may be integral with the light managementcomponent and/or the light delivery component.

The spacers occupy only a portion of the entry surface of the lightmanagement component. For example, it may be preferred that the voidsoccupy half or more of the entry surface of the light managementcomponent. In another example, it may be desired that the voids occupy90% or more of the entry surface of the light management component whilethe spacers occupy the remaining 10% or less of the entry surface of thelight management component. Alternatively, the voids occupy 95% or moreof the entry surface of the light management component while the spacersoccupy 5% or less of the entry surface of the light managementcomponent. As such, a significant portion of the entry surface of thelight management component is occupied by the voids such that therefraction characteristics of light entering the light managementcomponent through the entry surface are retained even though the lightdelivery component is integrated with the light management component.

As will be seen below, the voids may be defined by a variety ofstructures interposed between the light management component and thelight delivery component. As such, the voids may be defined as includingan exit surface proximate the light management component, i.e., asurface through which light exits the void before reaching the entrysurface of the light management component. Although the exit surface ofthe void and the entry surface of the light management component may becoincident or the same (see, e.g., FIGS. 1 & 3), in some instances theyare not. For example, FIGS. 5 & 6 depict examples in which the exitsurface of the void is not the same as the entry surface of the actuallight management component.

Similarly, the voids may be defined as including an entry surface, i.e.,a surface through which light enters the void after exiting the lightdelivery component. Although the entry surface of the void and the exitsurface of the light delivery component may be coincident or the same(e.g., see FIG. 1), in some instances they are not. For example, FIGS.3-5 depict examples in which the exit surface of the actual lightdelivery component and the entry surface of the voids are not the same.

FIG. 1 is a partial cross-sectional view of one illustrative opticalassembly according to the present invention. The optical assembly 10includes a light management component 20 attached to a light deliverycomponent 30 in the form of a diffusing body. Voids 41 are definedbetween the light management component 20 and the light deliverycomponent 30 such that a significant portion of the entry surface 24 isoccupied by the voids 41. As used in connection with the presentinvention, the attachment between the light management component 20 andlight delivery component 30 may be adhesive, with the adhesive being apressure sensitive adhesive or any other adhesive, such as a curableadhesive.

Light management component 20 may take a variety of forms, although thedepicted light management component 20 includes an array of prisms 22 onthe opposite side of the light management component from its entrysurface 24. As such, the light management component 20 may have aprismatic structured surface such as those described above (e.g., BEF,etc.). The light management component 20 may be made of any suitabletransparent material having an index of refraction greater than that ofair, although it may be desired that materials with higher indices ofrefraction be used, such as, e.g., polycarbonate (with an index ofrefraction of 1.586).

Some examples of suitable light management component constructions withprismatic structured surfaces may include, but are not limited to,Brightness Enhancement Film (BEF I or BEF II), Transparent Right AngleFilm (TRAF), Optical Lighting Film (OLF or SOLF), or Diamond GradeSheeting, all of which are available from 3M Company, St. Paul, Minn.Other examples of light management component constructions may includethe rounded peak/valley films described in U.S. Pat. Nos. 5,394,255 and5,552,907 (both to Yokota et al.).

As seen in FIG. 1, it may be preferred that the entry surface 24 of thelight management component be substantially smooth such that refractionof light into the light management component 20 through the entrysurface 24 is uniform. The depicted light delivery component 30 includesa bottom surface 34 facing away from the light management component 20.As used herein, relational terms such as “top,” “bottom,” “side,” etc.are used only to facilitate understanding of the illustrativeembodiments in connection with the figures and those terms should not beconstrued to limit the scope of the invention unless explicitlyrequired. The depicted bottom surface 32 is smooth. It is not requiredto be smooth.

In the depicted construction, the spacers 40 are formed as a unitaryconstruction with the light delivery component 30. As used herein, a“unitary construction” is one in which the spacers 40 and the lightdelivery component 30 are formed from a continuous mass of material asin, e.g., a molding, thermoforming, casting, or similar process.Alternative constructions for the spacers 40 in optical assembliesaccording to the invention are described below.

Another feature depicted in FIG. 1 is that only a portion of the entrysurface 24 is occupied by the spacers 40 that are located between thelight delivery component 30 and the light management component 20. Asnoted above, the spacers 40 may occupy 10% or less (or in some instances5% or less) of the area of the entry surface 24. Those areas in whichthe spacers 40 are in direct contact with the entry surface 24 may stillrefract light. Alternatively, the light incident upon the entry surface24 in the areas occupied by the spacers 40 may be reflected away fromthe entry surface 24 or it may be absorbed (if, for example, anabsorbing material is located at the interface of the entry surface 24and the spacers 40).

Limiting the portion of the entry surface 24 occupied by the spacers 40preferably increases the area free of contact with the spacers 40. Thoseareas of the entry surface 24 that are not occupied by the spacers 40may be defined as voids 41. Within the voids 41, it may be preferredthat the entry surface 24 be exposed to air such that an air/entrysurface interface is formed to retain the refractive characteristics ofthe light management component 20.

In addition to occupying only a portion of the entry surface 24 of thelight management component 20, the spacers 40 are preferably distributedover the entire entry surface 24. In other words, the spacers 40 arepreferably not restricted to, e.g., the edges of the entry surface 24.It may be more preferred that the spacers 40 be uniformly distributedover the entry surface 24 of the light management component 20. Althougha uniform distribution may be preferred, the spacers 40 may be providedin a regular pattern, irregular pattern, random distribution, etc.

In a similar manner to their relationship with the entry surface 24 ofthe light management component 20, the spacers 40 may also occupy only aportion of the exit surface 32 of the light delivery component 30.Although the spacers 40 are depicted in FIG. 1 as having a uniformcross-section such that they occupy the same amount of the exit surface32 of the light delivery component 30 as they occupy of the entrysurface 24 of the light management component 20, that relationship isnot required. In other words, the spacers 40 may occupy the same portionof the exit surface 32 as they do of the entry surface 24, or they mayoccupy more or less of the exit surface 32.

The shape, size and lateral spacing distance of the spacers 40 may vary.For example, the spacers may be formed as posts (e.g., round, square,triangular, elliptical, irregularly shaped, etc.) that occupy discreteareas of, e.g., the entry surface 24. Alternatively, the spacers 40 maybe formed as ribs or other elongated structures that extend from, e.g.,edge-to-edge, over the optical assembly. In some embodiments, post-likestructures and rib-like structures may be combined.

Although the spacers 40 may be provided as discrete structures (e.g.,posts, ribs, etc.), in other embodiments the spacers 40 may be providedin the form of cells, e.g., hexagonal, triangular, square, rectangular,etc., with each cell defining one of the voids 41. In such a design,each of the voids 41 may be independent, with substantially no fluidcommunication between the voids 41. In other embodiments, e.g., wherespacers 40 are posts or other structures that do not form independentvoids 41, the voids 41 may be interconnected. Characterized in anothermanner, the plurality of voids 41 depicted in FIG. 1 may actually beportions of one large void in which the spacers 40 are located.

Furthermore, shape variations in the spacers may be seen betweendifferent optical assemblies and/or within the same optical assembly.Further, the size of the spacers may vary, both between differentoptical assemblies and within the same optical assembly. Also, lateraldistance between the spacers may also vary between different opticalassemblies and/or within the same optical assembly. Regardless ofvariations in shape, size, and lateral distances, the amount of surfaceare occupied by the spacers 40 preferably remains within the limitsdescribed above. Also, the variations in shape, size, and/or spacing maybe provided to reduce or prevent undesired optical effects, e.g., moire,etc.

For purposes of the present invention, the exit surface 32 of the lightdelivery component 30 is defined as a surface above which the spacers 40are located, even though in some embodiments the exit surface 32 may notbe exposed or may be only minimally exposed. In FIG. 1, due to theunitary construction of the spacers 40 and the light delivery component30, the exit surface 32 can be characterized as extending underneath thearea occupied by the spacers 40 (indicated by broken lines underneatheach spacer 40 in FIG. 1. That principle is illustrated in FIG. 2, inwhich the light delivery component 130 of the optical assembly 110includes spacers 140 that occupy substantially all of the exit surface132 of the light delivery component 130. The tapered shape of thespacers 140, however, ensures that they occupy only a portion of theentry surface 124 of the light management component 120.

Returning to FIG. 1, in addition to occupying only a portion of theentry surface 24 of the light management component 20 and defining voids41 in which an air interface is maintained, the spacers 40 alsopreferably provide a structure by which the light management component20 and the light delivery component 30 can be attached to each other. Inthe embodiment of FIG. 1, the portions of the spacers 40 in contact withthe entry surface 24 of the light management component 20 may include anadhesive 42 or other bonding composition that attaches the spacers 40 tothe entry surface 24. Suitable adhesives may include, for example,pressure sensitive adhesives, curable adhesives, solvent-basedadhesives, etc. The adhesive may be optically clear, diffusive,absorptive, reflective, etc. as desired.

As discussed above, the light delivery component 30 of the depictedembodiment diffuses light before it enters the entry surface 24 of thelight management component 20. As used herein, the terms “diffuses,”“diffusion” and variations thereof mean that light changes direction asit passes through the light delivery component 30 from the directionalong which it approached the light delivery component 30. The changesin direction may preferably be such that features located on theopposite side of the light delivery component 30 from the lightmanagement component 20 cannot be visually discerned by the naked humaneye.

The diffusion provided by the light delivery component 30 may be closeto Lambertian (where the diffused light is substantially uniform in alldirections from zero to 90 degrees from a normal axis) or anisotropic asdiscussed in, e.g., U.S. Pat. No. 6,381,068 to Harada et al. Thediffusion may or may not be wavelength dependent. In addition, thediffusion may or may not be polarization sensitive, i.e., the diffusionmay occur for light of all polarization orientations or the diffusionmay be selective for light of one or more polarization orientations.Examples of polarization sensitive diffusion and articles to accomplishthe same may be described in, for example, U.S. Pat. Nos. 6,111,696 &6,239,907 (both to Allen et al.).

The light delivery component 30 may exhibit a variety of opticalproperties. These optical properties may be selected to complement theoptical properties of the light management component 20 and any otheroptical components through which the light will reach after passingthrough the light delivery component 30. The optical properties that maybe exhibited by the light delivery component 30 include, but are notlimited to, relatively high forward transmission of incident light (ifthe light delivery component is a diffuser) and polarizationpreservation for light passing through the light delivery component 30to the light management component 20.

The first optical property listed above, high forward transmission oflight, e.g., transmission of not less than about 70%, more preferablynot less than about 80%, of incident light, can prevent or reducereflection of ambient light from the light delivery component 30 beforethe light reaches the light management component 20. The high forwardtransmission may be exhibited for light traveling in both directionsthrough the light delivery component 30, or it may be higher in onedirection.

Another optical property that may be exhibited by a light deliverycomponent 30 used in connection with the present invention ispolarization preservation. In other words, the light delivery componentmay not convert or otherwise affect the polarization state of asubstantial portion of the light passing through the light deliverycomponent 30 towards the light management component 20. This opticalproperty may be useful in connection with optical components that relyon the polarization of properties of light, e.g., Liquid Crystal Display(LCD) devices, etc.

The depicted light delivery component 30 is a bulk diffuser includingbulk diffusing particles 36 incorporated into the light deliverycomponent 30 to provide the desired diffusion of light. Although notrequired, the spacers 40 may also include the bulk diffusing particles36. Furthermore, if desired, adhesive 42 provided between the spacers 40and the entry surface 24 of the light management component may also actas a diffuser. Alternatively, the adhesive 42 may be optically clear.Bulk diffusers may include a transparent base material and at least onelight-diffusing material, such as a pigment and/or beads, dispersed inthe transparent base material. The pigments used may include a whitepigment (for example, titanium oxide) and may also include one or morecolored pigments, e.g., carbon black.

FIG. 3 depicts another embodiment of an optical assembly according tothe present invention. The optical assembly 210 includes an lightmanagement component 220 and a light delivery component 230 separated byspacers 240 and voids 241. The spacers 240 in this embodiment areunitary with the light management component 220 rather than the lightdelivery component 230 as in the embodiments depicted in FIGS. 1 and 2.Similar to the embodiments described above, the spacers 240 occupy onlya portion of the entry surface 224 of the light management component220.

In a difference from the embodiment depicted in FIG. 1, the exit surface232 of the light delivery component 230 includes adhesive 242 or anotherbonding composition that attaches the spacers 240 to the exit surface232. Suitable adhesives may include, for example, pressure sensitiveadhesives, curable adhesives, solvent-based adhesives, etc. The adhesivemay be optically clear, diffusive, etc. as desired. It should be noted,however, that if the adhesive 242 covers significant portions orsubstantially all of the exit surface 232 of the light deliverycomponent 230, it preferably transmits significant portions of the lightincident on the exit surface 232 from within the light deliverycomponent 230.

FIG. 4 depicts another illustrative embodiment of an optical assembly310 according to the present invention. The optical assembly 310includes a light management component 320 with an entry surface 324.Spacers 340 are attached to the entry surface 324. The spacers 340 are,themselves, attached to each other through a base layer 346. The baselayer 346 is itself attached to another substrate 330. It should beunderstood, however, that substrate 330 is optional. In the embodimentdepicted in FIG. 4, the spacers 340 and their base layer 346 serve as abulk diffuser of light entering the light management component 320through its entry surface 324. In the depicted embodiment, the materialsused to form the spacers 340 and base layer 346 includes diffusingparticles 336 located therein. As a result, light passing through thematerials of spacers 340 and base layer 346 is diffused before reachingthe entry surface 324 of light management component 320.

FIG. 5 depicts another embodiment of an optical assembly 410 accordingto the present invention. The optical assembly of FIG. 5 includes twolight management components 420 and 470. As depicted, the lightmanagement components 420 and 470 include prismatic structured surfaces,such as, e.g., BEF. In the embodiment of FIG. 5 the prismatic structuresare depicted as having a crossed configuration, in other words theprisms are not aligned (with the broken line in light managementcomponent 470 depicting the valley located between each of the prisms inlight management component 470).

The optical assembly of FIG. 5 also includes a plurality of spacers 440located between a light delivery component 460 and the light managementcomponent 420. The spacers 440 are depicted as attached to a base layer450 although they may be integral with that layer (as seen in FIG. 4).Layers of adhesive 442 and 444 are located on each side of the spacers440 and base layer 450. Adhesive layer 442 is used to attach the baselayer 450 two light management component 420. Adhesive 444 attaches thespacers 440 to the light delivery component 460. In this embodiment, itmay be desirable that the materials used for base layer 450 and adhesive442 have an index of refraction that substantially matches that of thematerials used for light management component 420. As a result, lightentering the light management component 420 can be properly refracted.Adhesive layer 444 may beneficially diffuse light passing from lightdelivery component 460 into the voids between spacers 440.

FIG. 6 depicts another optical assembly according to the principles ofthe present invention. The optical assembly 510 includes a lightmanagement component 520 with an entry surface 524. Also included inoptical assembly 510 are spacers 540 attached to a base layer 550. Inthe depicted embodiment, the base layer 550 is unitary with the spacers540. The spacers 540 are each attached to the surface 562 of a lightdelivery component 560 located at the bottom of optical assembly 510 asseen in FIG. 6.

Light delivery component 560 may be, e.g., a light guide with thecontact points between spacers 540 and surface 562 of the light deliverycomponent 560 serving as extraction points at which light is extractedfrom the light delivery component 560. The extracted light can travelinto the light management component 520 through its entry surface 524.In this embodiment, it may be desired that the materials used for baselayer 550 and spacers 540 have an index of refraction that issubstantially matched with the index of refraction used to manufacturethe light management component 520. Also depicted in this embodiment arediffusing particles 536 located within the materials used to manufacturebase layer 550 and spacers 540. As such, light exiting the optical body560 and entering the light management component 520 through its entrysurface 524 can be diffused.

Still another optical assembly is seen in FIG. 7 where optical assembly610 includes a light management component 620 at its top and a lightdelivery component 660 at its bottom. As in the embodiment depicted inFIG. 6, optical assembly 610 may, for example, including light deliverycomponent 660 in the form of a light guide. As a result, spacers 640located in contact with surface 662 of light delivery component 660 maybe used to extract light as it moves through the light guide of lightdelivery component 660. Spacers 640 are formed integral with a baselayer 650 which also includes spacers 640 on its opposite side, in otherwords, the side of base layer 650 that faces entry surface 624 of lightmanagement component 620.

The base layer 650 and/or the spacers 640 may preferably includediffusing particles 636 or otherwise act to diffuse light exiting thelight delivery component 660 and entering light management component 620through its entry surface 624. One potential advantage of theconstruction seen in FIG. 7 is that a plurality of voids are maintainedover entry surface 624 such that it may not be required to match theindex of refraction between the material used for light managementcomponent 620 and base layer 650 (as in optical assembly 510 describedabove).

Optical assembly 710 as seen in FIG. 8 illustrates other features thatmay be suitable for use in connection with the present invention. Forexample, the spacers 740 located between a base layer 750 and lightmanagement component 724 may include a reflective layer 748 proximatepoints at which the spacers 740 contact the entry surface 724 of lightmanagement component 720. The reflective layer 748 may be in the formof, e.g., a metallized layer or other reflective material. In thedepicted embodiment, the spacers 740 are attached to the entry surface724 of light management component 720 through a layer of adhesive 742.One potential advantage of the construction seen in FIG. 8 is that lightmay be prevented from passing directly from the interior of the spacers740 into the light management component 720.

The plurality of spacers 740 are attached to a base layer 750 which is,in turn, attached to an optional light delivery component 760. It may bepreferred that the base layer 750 be diffusing or that light from thelight delivery component 760 be diffuse before passing into the spacers740 or the voids formed by spacers 740 between base layer 750 and lightmanagement component 720.

FIG. 9 depicts an optical assembly 810 that includes a light managementcomponent 820 and a light delivery component 860. The base layer 850 andspacers 840 are located between the light management component 820 andthe light delivery component 860. Spacers 840 define voids between baselayer 850 and the entry surface 824 of the light management component820. Also seen in FIG. 9 are a plurality of diffusing particles 838located on the surfaces of base layer 850 between spacers 840.

The diffusing particles 838 may be replaced, in some instances, by,e.g., another surface diffuser or other structured surface such as amicrostructured surface, an optically rough surface etc. In suchinstances, it may be preferred that the particles 838 or other structure(at what can be referred to as the entry surfaces of the voids 841) bean air interface (or other gas) such that the refraction of light as itenters the voids 841 is not disturbed by a lower refraction index ratio.

Another optional feature depicted in FIG. 9 it is the use of a layer ofreflective material 870 on the sides of spacers 840. The reflectivematerial 870 may prevent light exiting the base layer 850 between thespacers 840 from subsequently entering the spacers 840 through theirside surfaces (i.e., the surfaces on which the reflective material 870is located). In addition, it may be advantageous to provide thereflective material 870 between the spacers 840 and entry surface 824 oflight management component 820 in a manner similar to that depicted inconnection with FIG. 8.

FIG. 10 depicts another optical assembly 910 that also includes a lightmanagement component 920 with an entry surface 924. Spacers 940 areattached to the entry surface 924 of light management component 920 in amanner that forms voids between the spacers 940 and a light deliverycomponent 930 located beneath the spacers 940. It may be preferred thatthe light delivery component 930 be a diffusing structure such thatlight passing through light delivery component 930 is diffused beforereaching entry surface 924 of light management component 920.

Optical assembly 910 as depicted in FIG. 10 includes to rays of light970 and 972 that are provided to illustrate an alternative way toprevent light within the voids formed between spacers 940 fromreentering the spacers 940. For example, ray 970 exits a spacer 940 andenters the void located between spacers 940 and entry surface 924. Whilein that void, ray 970 enters the adjacent spacer 940, where it isrefracted and reflected back into light delivery component 930.

Ray 972 exits light delivery component 930 and enters one of the spacers940. Ray 972 exits the spacer 940 into the void formed by spacers 940with entry surface 924. The ray 972 is incident on a side surface ofspacer 940 body and is reflected off of that side surface where it isincident on entry surface 924 of light management component 920. Ray 972is then refracted into the light management component 920 at thatlocation. In this embodiment, the geometry of the spacers and materialsselected for them are such that at least a substantial portion of lightis prevented from entering the side surfaces of spacers 940 byreflection in the absence of a reflective coating as used in opticalassembly 810 described above.

An optical assembly 1010 is depicted in connection with FIG. 11 andincludes a light management component 1020 separated from a lightdelivery component 1030 by a plurality of spacers 1040. The spacers 1040are, in the depicted embodiment, in the form of spheres or beads whichmay themselves be transmissive or reflective. Each of the spacers 1040is depicted as coated with a layer of adhesive 1042 such that thespacers 1040 attach the light delivery component 1030 to the entrysurface 1024 of light management component 1020. In the depictedembodiment, the light passing through light delivery component 1030 isdiffused by, e.g., diffusing particles 1036 located within lightdelivery component 1030. As such, light exiting the light deliverycomponent 1030 through its exit surface 1032 is diffused before itenters the entry surface 1024 of light management component 1020.

FIG. 12 depicts an optical assembly 1110 that includes a lightmanagement component 1120 and a light delivery component 1130 separatedby spacers 1140 and voids 1141. In the depicted embodiment, the spacers1140 are in the form of beads, between which voids 1141 are formedbetween light delivery component 1130 and light management component1120. Light delivery component 1130, in the depicted embodiment,includes light diffusing particles 1136, although the diffusingparticles may be optional.

Also seen in the FIG. 12 is a layer of adhesive 1142 located on entrysurface 1124 of light management component 1120. The adhesive layer 1142may preferably be optically clear such that light refracting through theadhesive layer 1142 is not diffused. Another layer of adhesive 1146 islocated on exit surface 1132 of light delivery component 1130. The twolayers of adhesive 1142 and 1146 operate with spacers 1140 to connect orattach light management component 1120 to light delivery component 1130while maintaining voids 1141 between the spacers 1140.

In contrast with the adhesive 1142, adhesive layer 1146 located on exitsurface 1132 of light delivery component 1130 may diffuse light exitingexit surface 1132 and traveling towards the entry surface 1124 of lightmanagement component 1120. Furthermore, spacers 1140 may be transmissiveor reflective as needed to obtain desired optical properties for theoptical assembly 1110.

FIG. 13 depicts one embodiment of an optical display system thatincludes an optical assembly 1210 according to the present invention inconnection with various other components to obtain a desired opticalresult, e.g., display an image to a viewer. For example, the opticalsystem of FIG. 13 includes a light guide 1290, a light source 1292, anda reflector 1294, adapted to reflect light from light source 1292 intolight guide 1290. Light guide 1290 is preferably manufactured ordesigned to distribute light over its surface 1292 such that the lightenters optical assembly 1210 (which may include a variety of componentsas described above). The system also includes a back reflector 1296positioned to reflect light escaping from the back side of the lightguide 1290.

The light, after passing from light guide 1290 into optical assembly1210, enters a display component 1280 that may be, for example, a liquidcrystal display or similar device that requires light to provide animage or other effect. It will be understood that optical assembly 1210may include one or more light management components (see, for example,FIG. 5). Furthermore, it will be understood that the optical assembly1210 may be fixedly attached to the light guide 1290 as seen in, forexample, FIG. 6.

The materials and techniques used to manufacture the components such aslight management components, light delivery components, light guides,etc. will be well known to those of skill in the art. For example, lightguide 1290 and associated light source 1292 and reflector 1294 may bereplaced by an electroluminescent panel, additional components such asback reflectors, reflective polarizers, etc. may be included in theoptical display system. For some relevant discussions regarding opticaldisplay systems and the components that may be included in them, see,e.g., U.S. Pat. No. 5,268,782 (Wenz et al.); U.S. Pat. No. 5,394,255(Yokota et al.); U.S. Pat. No. 5,552,907 (Yokota et al.); U.S. Pat. No.5,825,542 (Cobb, Jr. et al.); U.S. Pat. No. 5,917,664 (O'Neill et al.);U.S. Pat. No. 6,052,164 (Cobb, Jr. et al.); U.S. Pat. No. 6,091,547(Gardiner et al.); U.S. Pat. No. 6,111,696 (Allen et al.); U.S. Pat. No.6,117,530 (Jonza et al.); U.S. Pat. No. 6,166,797 (Bruzzone et al.);U.S. Pat. No. 6,239,907 B1 (Allen et al.); and U.S. Pat. No. 6,356,391B1 (Gardiner et al.).

The spacers and associated structures (e.g., base layers) used to definethe voids between the light management components and the light deliverycomponents of optical assemblies according to the invention may,however, be formed of materials that may differ from those commonly usedin the manufacture of optical components. It may be desired, forexample, that the spacers and/or associated structures exhibit someadhesive properties when they are used to attach light deliverycomponents or other structures to the entry surface of a lightmanagement component. Further, the materials used for the spacers andassociated structures preferably retain a desired structure both duringmanufacturing and as a finished product.

In some embodiments, it may be desirable to use an adhesive that can bereferred to as a structural hybrid adhesive with two stages. In a firststage, the structural hybrid adhesive may exhibit characteristicscommonly associated with pressure sensitive adhesives. In the firststage, the materials may be relatively soft such that long term storageor use may degrade any structures formed in the material. In a secondstage, however, the structural hybrid adhesive may be cured such that itretains a desired structure and at least some of the adhesive propertiesof the first stage such that any structures attached to be structuralhybrid adhesive during its first stage remain attached after thestructural hybrid adhesive has been cured to its second stage. As usedin connection with the present invention, the term “curable” means amaterial that undergoes an irreversible change in modulus after exposureto one or more of a curing agent, heat, and/or radiation. The term“radiation” includes actinic radiation such as, e.g., electromagneticradiation in the UV or visible range of the electromagnetic spectrum,electron beam radiation, etc. Such curable materials may include variouscomponents such as diffusing particles, conductive particles, fibers,etc. to provide desired optical or other properties.

Structural hybrid adhesives may be formed into the desired structures(e.g., spacers as seen in connection with many of the embodimentsdescribed above) by the use of casting, embossing, micro-embossing, orany other suitable technique. If embossed or micro-embossed, thestructures may be formed using an embossed or micro-embossed liner thatincludes a layer of release material (material to which the structuralhybrid adhesive exhibits low adhesion).

In place of forming the spacers and associated structures from astructural hybrid adhesive, the spacers and associated structures may beformed using a multilayer system as illustrated in FIGS. 14A-14C. Asseen in FIG. 14A, the multilayer system includes a layer 1448 of curablematerial on a backing 1460. The backing 1460 may be, e.g., a polymericfilm, glass, metal or any other suitable substrate on which the layer1448 of curable material can be located. A layer of pressure sensitiveadhesive 1442 is also included in the multilayer system, with the layer1448 of curable material being located between the pressure sensitiveadhesive 1442 and the backing 1460. Although only three layers aredepicted, it will be understood that a multilayer system could includemore layers than those depicted in FIG. 14A.

The term “pressure sensitive adhesive” as used herein refers to acategory of adhesives that, in solvent-free form, are aggressive andpermanently tacky at room temperature and firmly adhere to a variety ofdissimilar surfaces upon contact without the need of more than finger orhand pressure. They require, for example, no activation by a curingagent, heat, radiation or solvent to exert a strong holding force towardmaterials such as paper, plastic, glass, wood, cement, and metals.

Turning to FIG. 14B, the multilayer system of FIG. 14A is embossed orotherwise deformed such that the curable material 1448 is formed into astructure that includes spacers 1440 and a base layer 1450. Theembossing may be performed using, e.g., a structured liner 1480 thatincludes recesses in the shape of the desired spacers 1440. Thisembossing is preferably performed before the curable material of layer1448 is cured such that the structure of the liner 1480 is essentiallyreplicated by the pressure sensitive adhesive 1442 and curable material1448. It may be preferred that the pressure sensitive adhesive 1442retain its integrity during deformation of the curable material 1448such that, after deformation, the spacers 1440 and associated base layer1450 are covered by the layer of pressure sensitive adhesive 1442.Alternatively, it may be sufficient if only the spacers 1440 retain thepressure sensitive adhesive 1442.

With the structures thus formed in FIG. 14B, the curable material iscured such that the spacers 1440 and base layer 1450 retain theirstructural integrity. In some instances, the curing may be only partial,such that the structures may be retained during further manufacturing,with complete curing being performed.

After sufficient curing to retain the structures seen in FIG. 14B, theliner 1480 is removed and the spacers 1440, base layer 1450 and attachedbacking 1460 are attached to the entry surface 1424 of an lightmanagement component 1420. If the curable material 1448 was onlypartially cured after deformation to form the spacers 1440, then curingmay be completed after attachment to the light management component1420.

In connection with the multilayer system of FIGS. 14A-14C, differentlayers may include various components such as diffusing particles,conductive particles, fibers, etc. to provide desired optical or otherproperties. For example, the curable material may include diffusingparticles dispersed therein, the backing 1460 may include diffusingparticles, etc.

The approaches to providing adhesive structures described above may befurther supplemented by the discussions of the microstructured linersand pressure sensitive adhesives that can form adhesive structures asdescribed in, e.g., U.S. Pat. No. 6,197,397 B1 (Sher et al.).Furthermore, processes and materials for providing curable adhesivesthat may be used in connection with the invention may also be describedin U.S. patent application Ser. No. 10/157260, titled SEGMENTED CURABLETRANSFER TAPES, filed on May 28, 2002 (Attorney Docket No. 57779US002);U.S. patent application Ser. No. 10/005,669, titled HYBRID ADHESIVEARTICLES AND METHODS, by Yang et al., filed Nov. 2, 2001; PCTPublication No. WO03/102101, titled ADHESIVE TAPE, filed on May 28, 2002(Attorney Docket No. 56172WO002) on behalf of 3M Innovative PropertiesCo. as applicant; and U.S. Provisional Patent Application Ser. No.60/383756, titled CURABLE ADHESIVES STRUCTURES, filed on May 28, 2002(Attorney Docket No. 57863US002).

When curable structural hybrid adhesives are used to manufacture anoptical assembly according to the present invention, it may beadvantageous to supply the structural hybrid adhesives on a releaseliner, e.g., a structured liner, with the curable adhesive attached tothe entry surface of the light management component. One such embodimentis depicted in FIG. 15, with the curable adhesive 1540 located between alight management component 1520 and a structured release liner 1548.When eventually removed from the construction, the structures 1543 ofthe release liner 1548 separating portions of the curable adhesive 1540will form the voids described in the constructions above. The curableadhesive 1540 may preferably not be fully cured, such that afterremoving the release liner 1548 (and leaving the curable adhesive 1540attached to the entry surface 1524 of the light management component1520), the curable adhesive 1540 can be attached to a light deliverycomponent (see above) and cured to form an optical assembly including alight management component 1520 and a light delivery component andassociated voids located therebetween.

In another embodiment depicted in FIG. 16, curable adhesive 1640 islocated between a light management component 1620 and a liner 1648. Thecurable adhesive 1640 preferably defines voids 1641 between the entrysurface 1624 and the liner 1648. The curable adhesive 1640 in thisembodiment may be (but is not necessarily) fully cured because theconstruction includes a layer of pressure sensitive adhesive 1642between the curable adhesive 1640 and the liner 1648. After removing theliner 1648, the pressure sensitive adhesive 1642 can be used to attachthe curable adhesive 1640 to a light delivery component (see above),thereby providing an optical assembly including a light managementcomponent 1620 and a light delivery component and associated voidslocated therebetween.

In those embodiments involving a release liner, curable adhesive andlight management component, methods of manufacturing an optical assemblyaccording to the present invention may involve laminating the curableadhesive and liner combination to a light management component, followedby stripping the liner and laminating the opposite side of the curableadhesive to a light delivery component. Either or both laminations maybe followed by at least some curing of the curable adhesive, witheventually complete curing of the curable adhesive.

All references and publications cited herein are expressly incorporatedherein by reference in their entirety into this disclosure. Illustrativeembodiments of this invention are discussed and reference has been madeto possible variations within the scope of this invention. These andother variations and modifications in the invention will be apparent tothose skilled in the art without departing from the scope of theinvention, and it should be understood that this invention is notlimited to the illustrative embodiments set forth herein. Accordingly,the invention is to be limited only by the claims provided below.

1. An optical assembly comprising: a light management componentcomprising first and second structured major surfaces having periodicstructures with a same pitch; and a light delivery component comprisingan exit surface attached to the second structured major surface at oneor more attachment points, the one or more attachment points definingunfilled voids located between the exit surface and the secondstructured major surface, wherein one or both of the light managementcomponent and the light delivery component exhibit an optical gain ofone or more.
 2. The optical assembly of claim 1, wherein at least onestructure in the first structured major surface comprises a curvedfacet.
 3. The optical assembly of claim 2, wherein the at least onestructure has a cross section of a convex arc.
 4. The optical assemblyof claim 1, wherein at least one structure in the second structuredmajor surface is rectangular.
 5. The optical assembly of claim 1,wherein at least one structure in the second structured major surface isoptically diffusive.
 6. The optical assembly of claim 1, wherein atleast one structure in the second structured major surface comprises acolored pigment.
 7. The optical assembly of claim 6, wherein the coloredpigment is a white pigment.
 8. The optical assembly of claim 1, whereinat least one structure in the second structured major surface comprisesan adhesive.
 9. The optical assembly of claim 1, wherein the lightdeliver component comprises a diffuser.